/* 层级大小
[z-normal]{
  z-index:1;
}

[z-top]{
  z-index:1000;
}

[z-popper]{
  z-index:2000;
}

----------------------*/
@each $style in (normal $index-normal, top $index-top, popper $index-popper) {
  [z-#{nth($style,1)}] {
    z-index: #{nth($style,2)};
  }
}
